US1951943A - Method of producing printing images - Google Patents

Description

March 20, 1934.

H. T. MossB'l-:RG

METHOD OF PRODUCING PRINTING IMAGES Filed April 9, 1928 pere/W27; /f// A C50/17 Arab/'c Pri/wary [maya @MQM @i Patented Mar. 20, 1934 UNITED STATES PATENT OFFICE METHOD OF PRODUCING PRINTING IMAGES Application April 9, 1928, Serial No. 268,815

11 Claims.

- 'This invention relates to the art of printing and more particularly to the formation and composition of printing surfaces or images.

ThisI is in part a substitute of applicants prior application Serial No. 4,176, filed January 23,

1925, which has been abandoned.

Among other objects, the invention is intended to provide printing surfaces or images of great durability, susceptible of being produced by simple and economical procedure. I The present inventive subject-matterv embraces both method and product.

The invention is illustrated in the accompanying drawing, in which Figures 1 to 9, inclusive, are sections of my improved printing device at the several stages of its preparation.

For the purpose of explaining the character of the invention, one illustrative method, eventuating in an exemplary product, will be described as 20 founded upon some of the preliminary steps of a well-known lithographie process. derstood, however, that the lithographie process referred to is by no means essential to the use of either the method or the product invention.

When the method begins with the illustrative conventional practice, a metal plate (e. g., .of zinc or aluminum) is provided with a light-sensitive albumin film which is exposed to some sort of a photographic process, as by being exposed to light through a photographic negative. A so-called developing ink (e. g., a turpentine developing ink) is applied over the entire surface of the previously exposed albumin lm, after which the whole is developed in water -which removes the albumin film and its coating of developing ink excepting only those parts that were exposed to light. This residue of the albumin film and its coating of developing ink, remains as the first stage in the production of the image which is to be employed in printing.

Still following a well-known practice, the entire surface of the plate is wiped over with a gum arabic solution which deposits a thin film of gum arabic over the area of the plate not occupied by o the preliminary image; but because the image is surfaced by the relatively greasy developing ink, the gum arabic does not adhere materially to the image.

At this stage, the product consists of the metal sheet, the adhered image having the albumin body surfaced by the developing ink, and the gum arabic coating on the exposed surface of the plate not occupied by the image. It is to this intermediate product that the initial step may be It is to be un,

applied in the illustrative method embodying present invention.

For this purpose, the developing ink (which has served its purpose of repelling the gum arabic coating throughout the area of the image) is Washed from the image with turpentine or the like while leaving the albumin body of the image intact but substantially uncovered. Then, over the entire surface of the plate and image, is applied (for instance, by means of a rag) a thinlayer of a so-called primary coating composed in accordance with this invention as presently described. Thereupon the surface of the plate is Washed with Water with the result that the gum arabic and its layer of the primary coating are removed, while the image, being repellent to water, is left adhering to the metal plate and having its albumin body surfaced by the primary coating. Because of the thinness of the primary coating and the manner in which it is applied, it i does not form an impervious film over the gum arabic, and the water can penetrate to the gum arabic and thus remove the gum arabic and its layer of primary coating. The material of the primary coating itself, however, is insoluble in and repellent to water. .The primary coating when applied is preferably liquid enough substantially to impregnate and become incorporated with the more or less porous albumin; and the primary coating upon drying to some extent possesses a tacky surface. At this juncture, the intermediate product consists of the metal plate and the adhered image having the albumin body, and, incorporated therewith or at least securely cohering therewith, the primary coating.

This intermediate product is moistened (e. g., with Water) to prevent adhesion to the metal areas outside the image, of the so-called secondary coating (presently described) Which is insoluble in and repellent to water. This secondary coating is next applied preferably by means of a hand roller in the usual manner of rolling up, or inking, a lithographie plate, and it adheres to the image, the tacky and water-repellent surface of which assists in establishing an effectual bond with the secondary coating. The relatively heavy plastic but viscous body of the secondary coating permits application by means of a roller, and this preferred consistency of the secondary coating and method ,of application produce on the image aV relatively thick layer of the secondary coating.

While the primary coating may be non-essential in some aspects of the invention, as at present advised, it serves advantageously to secure reliably the together the albumin body and the secondary coating, and the eiiiciency of its performance is enhanced if the primary coating is well incorporated in the albumin body and has its surface tacky enough to secure eifectual cohesion with the secondary coating.

Next, the entire plate is wiped over with a gum arabic solution which deposits a film of gum arabic on the surface of the metal plate outside the area of the image; but the secondary coating is sufficiently repelient to the gum arabic solution (as by being somewhat greasy) so that the image remains uncovered by the gum arabic. One of the main purposes of this application of the gum arabic film is to protect the exposed metal plate against oxidation.

At this stage the intermediate product. 1n its more important aspect, comprises the plate and the adhering image having the albumin body surfaced with the secondary coating which is preferably bonded to the body by the primary coating.

'I'his intermediate product may be heated to a sufficient degree and for a sufcient period (as may be ascertained empirically by one skilled in the art) to drive oif such volatile constituents and in such amount, as may be necessary or desirable, to harden and to polymerize the secondary coating. For example, the intermediate product at the stage just referred to may be subjected to oven heat atapproximately 121 degrees C. for a period of from 11/2 hours upward. As it issues from this heat or other hardening treatment, the image presents a desirably hard and durable surface superior to those heretofore familiar in the art and capable of withstanding, Without material impairment of the image, a much greater number of impressions than can be withstood by the usual image formed in a lithographie or similar process. The product just described is now ready to be used for printing in a manner which wili be understood by those skilled in the art.

The primary and secondary coatings above referred to, and illustrative methods of making them, will be next described. The selected illustrative procedure is such that it produces both of these coatings, respectively, at successive stages, the secondary coating emerging as a product at a relatively early stage, and being then modified to produce the primary coating. It is to be understood, however, that this particular procedure and the selected ingredients and their proportions, about to be explained, are only exemplary. Various `equivalents of the ingredients will appear to those skilled in the art as will practicable variations in their proportions. And it is not important that the two coatings issue as successive products of a continued procedure; on the contrary, the sequence of operations and the selection of steps leading to the respective coatings or their equivalents may be variously modified as will appear to those skilled in the art.

A preferred first stage in the illustrative` procedure leading first to the secondary coating and then to the primary coating, has for its object the production of a synthetic resin. For this purpose, to 100 grams of crystalline phenol or its equivalent are added 3 grams of concentrated ammonia water and 90 grams of formaldehyde. This mixture is boiled in a reflux condenser to prevent the formaldehyde from being driven off in the process of boiling, which is continued for about three hours. Thereafter the mixture is cooled, and evaporated, preferably in an oven below 50 degrees C., to drive off moisture. After the evaporating, the residue is a resin product which may be further heated in a relatively low temperature oven to assure the elimination of objectionable moisture for instance, the residue of resin may bekept in an oven at a temperature of about 50 degrees C. for about 12 hours.

This resin produced as just described is in the form of a viscous varnish-like uid the degree of viscosity of which can be regulated by varying the duration of the boiling. It can be produced, for example, in any consistency from a watery liquidity up to a low degree of plasticity or even a solid state.V In the heat treatment following the evaporation, it is desirable to insure conditions which will drive out any undesirable moisture "but will avoid driving out any other constituent.

AWhile the concentrated ammonia water suggested above is a desirable and convenient condensing agent, others may be employed as may be selected by those skilled in the art.

According'to the theories thus for developed in reference to this invention, the following describes the probable development in the specific illustrative process just described as the rst stage in making the primary coating. The boiling of the combined phenol and formaldehyde starts a condensation process. This process is partially arrested or at least retarded (by terminating the boiling) while the combined ingredients are still fluid, and preferably in an early stage in the condensation process. If the treatment ended at this juncture, the condensation, though retarded, would nevertheless proceed, even at room temperatures, and the combination of ingredients `would become more and more viscous and finally would solidify. It is preferred, however, to arrest or at least to retard the progress of the synthetic resin toward solidity, and to that end, among other purposes, the next stage is employed.

To 60 grams of the above described synthetic resin are added 40 grams of diethyl phthalate, the latter serving as a plasticizing agent, retarding the drying and preventing a premature setting of the varnish-like resin. At this point the synthetic resin has attained the condition of a useful resin varnish.

The plasticizer being added to the still liquid resin. two desirable results ensue: first, the resinforming process is retarded or substantially arrested; and, second, since the resin is still in liquid form, a high concentration of the resin content in mixture with the plasticizer is made possible Without undesirably enhancing the viscosity of the mixture. The resulting intermediate product, besides having a high concentration of resin, may have stable liquidity over several months at least, according as the ingredients and their proportions and their treatment may be regulated by those skilled in the art.

Preferably, a further effort is made to insure stable liquidity of the plasticized resin thus far described, which is referred to hereinafter as the initial resin varnish (but with no intention of limitation or characterization) to distinguish it from the intermediate product next described.

For addition to this initial resin varnish, it is desirable to employ a resin that has no material tendency to harden at room temperatures. When a synthetic resin is employed for this purpose, one is preferably selected which has passed sub.- stantially through the resin-forming process and therefore has little if any tendency to harden further at room temperatures. This resin, conveniently treated in the form of a fine powder,

The above described initial resin varnish andthe plasticized Redmanol resin or its equivalent are mixed together in equal parts by weight.

Next, 100 grams of the mixture just described with 5 grams of methyl violet 2 B base (or nigrosine base) and 5 grams of carbon black, are ground together in an ink mill. The methyl violet 2 B base is illustrative of a constituent which will enhance the repellency to water and consequently the attractiveness to ink of the secondary coating. Highly desirable and characteristic qualities of the secondary coating when.

polymerized by heating, as earlier described, are its hard slick surface with, at the same time, high degree of repellency to water and attractiveness to ink. The carbon black is simply illustrative, on the one hand of a pigment which may be used if desired, and on the other hand, of a physical stabilizer to give body to the varnish and to supply the usual physical properties of the so-called printing inks now employed in the art. While the addition of the carbon black or other pigment or stabilizer is now considered desirab1e,it is not essential in all aspects of the invention'.

At this stage the secondary coating above referred to, has somewhat the character of a printing ink which has been ground-in a relatively heavy varnish and is a plastic but viscous product which, for all practical purposes, is substantially stable physically and chemically over an indefinite period. The addition of the plasticized Redmanol resin or its `equivalent may have reduced somewhat the resin concentration below that of the initial resin varnish, but this is unobjectionable as long as the mixture is intended to be applied as a relatively viscous coating. 'I'he mixture preferably has sufficient body so that it may be readily and effectively applied by means of a roller, as already described. When this secondary coating has been applied to form the printing image and preferably has been baked as already described, it becomes a hard and durable printing surface which at the same time takes ink readily in a lithographie press, and is insolublein all solvents except strong caustic alkalis.

Toproduce the primary coating, the foregoing procedure may be added to by thinning the secondary coating product, for instance by the addition of denatured alcohol. Since, however, the addition of the Redmanol resin or its equivalent has somewhat reduced the resin concentration below that of the original resin-varnish (which had about a sixty per cent. concentration of resin) it is desirable to restore some of the concentration before thinning; and for this purpose about 67 grams of the initial resin varnish may be added to about 50 grams of the secondary coating product; and the combined ll'l grams may be suitably thinned by the addition thereto of 175 grams of denatured alcohol (e. g. U. S. Government Standard Formula No. 5, which Iis' desirably free from benzol) together with 5 grams of a plasticlzer, preferably either diethyl phthalate or butyl oxalate.

The final product just described is the primary coating above mentioned and if produced in the manner and with the ingredients and proportions suggested, it is a bluish black and thin liquid which when applied to the albumin body of the image can impregnate the albumin to an adequate extent and become well enough incorporated therewith, while at the same -time providing, if desired, a tacky surface to form an enhanced bond with the secondary coating.

While the foregoing illustrative process has been explained in connection with the making of socalled machine-made lithographie plates starting with the exposure of a light-sensitive albumin, that starting point and the employment of machine-made plates are evidently non-essential, as will appear to those skilled in the art, because the starting point might well be any image of sultable constitution, or image-area, regardless of the manner in which it was produced.

There are various inventive features exemplified, respectively, in the successive stages of the procedure hereinbefore described, and illustrated in the various intermediate products. In other words, several different specific methods and products have been disclosed lin the foregoing specification. While it is desired to claim many of them generically herein, it is the intention to claim the various specific features of invention in separate divisional applications at appropriate time or times.

What I claim is:

1. As an article of manufacture, a printing device comprising, in combination, a plate; a somewhat porous image on the plate; an indurated coating on the image, of a phenolic condensation product; and a binder intermediate said image and coating, partially impregnating the image.

2. As an article of manufacture, a planographic printing device comprising, in combination, a plate; a body of albuminous material adhered to said plate and forming an image; a thin resinous coating on said image and partially impregnating it; and a heat-hardened coating thereon, to supply a printing surface, comprising a phenolic condensation product.

3. As an article of manufacture, a printing device comprising in combination, a plate, a somewhat porous image on the plate; a thin coating of a phenolic condensation product on said image, and partially impregnating it; and a heat-hardened coating thereon, insoluble in organic and inorganic solvents'excepting strong caustic alkalis.

4. As an article of manufacture, a planographic printing device comprising, in combination, a metal plate, a somewhat porous image-body thereon; and a phenolic condensation product partially impregnating the image-body and forming a relatively thick and hard coating on said imagebody to supply a printing surface.v

5. A method of forming a printing surface which is characterized by forming an image area on a plate, applying to the image area by rolling a plastic resinous material and indurating the material.

6. A method of forming a planographic printing surface which is characterized by applying to a previously formed image a plastic resinous material and heat-hardening the material.

7. A method of forming a printing image which is characterized by forming on a plate an image- 10. A method of forming a printing image which is characterized by forming an image body of a proteinaceous material; coating the body with a liquid phenolic condensation product; and applying thereto a plastic phenolic condensation product and subjecting the composite result to a heathardening process. l

11. A method of forming a planographic printing surface which is characterized by rolling upon a previously formed image a plastic resinous material highly repellent to water, and polymerizing the material, thereby supplying a hard and slick coating upon said image.

HERMAN T. MOSSBERG.

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